In the manufacturing of integrated circuits, dies are often bonded to other package components. To bond a die, solder bumps are first formed on the surface of the die. The solder bumps are then dipped in flux. Conventionally, the flux dipping is performed using a flux plate including a dipping cavity, which has the size of the die. Flux is held in the dipping cavity, and the die is dipped in the dipping cavity with the solder bumps facing down.
Conventionally, the dip height, that is, the height of the portions of the solder bumps dipped in the flux, is controlled by selecting the depth of the dipping cavity. To add flux into the dipping cavity after each dipping, a flux bowl is used. The flux bowl is a metal frame, with the bottom edge of the metal frame contacting the flux plate. The metal frame may have a rectangular top-view shape. The flux bowl is bottomless, and the flux is held in the flux bowl. Accordingly, the flux in the flux bowl also contacts the flux plate. To add the flux into the dipping cavity, the flux bowl slides over the dipping cavity, and hence the flux in the flux bowl falls into the dipping cavity. Excess flux is swept away by the flux bowl during the movement of the flux bowl, and hence the flux left in the dipping cavity has a top surface level with the top surface of the flux plate, and level with the bottom surface of the metal frame.
Since the dipping cavity has a fixed depth, if the dip height needs to be adjusted, the plate that is being used has to be replaced by a plate with a dipping cavity having a different depth. Furthermore, there is no way to accurately control the profile of the flux.
There are also other dipping plates having different shapes. For example, there are some disk-shaped plates, wherein the disk-shaped plates rotate along an axis during the flux dipping processes. Again, dipping cavities are located in the disks to hold the flux. Similarly, these types of flux plates cannot be used in the advanced control of the dipping process due to the fixed depth in the dipping cavities.